A wireless device may send data to other wireless devices by transmitting communication signals carrying encoded data. Transmit output power of the wireless device may vary due to transmitter configuration, proximity of the other wireless devices, and/or other operating conditions. For example, when a first wireless device transmits signals to a relatively nearby second wireless device, a relatively low transmit output power may be used. In contrast, when the first wireless device transmits signals to a relatively distant second wireless device, a relatively high transmit output power may be used. In addition, transmit output power limits may be set forth by specifications such as the IEEE 802.11 specification or a BLUETOOTH® specification from the BLUETOOTH Special Interest Group.
A wireless device may use a power amplifier to amplify the communication signals transmitted to the other wireless devices. Power amplifier efficiency is a measure of the ability of the power amplifier to convert source power (e.g., power supplied to the power amplifier) to transmit output power. Power amplifier efficiency may vary across a range of transmit output power levels. That is, a power amplifier may operate less efficiently at some transmit output power levels than at other transmit output power levels. Inefficient power amplifier operation may generate excessive heat and may reduce battery life of the wireless device.
Thus, there is a need to improve power amplifier efficiency in wireless devices, particularly when transmitting signals with multiple transmit output power levels.